What is a card?

This post is about ambiguity, but this post is not about Ambiguity. (Don't forget to look at the card topsy turvy as well. And don't forget to look at the card Topsy Turvy as well)

Okay, enough with the puns... at least if I don't find any others while writing... what I really want to write about is how overloaded the term "Card" is in Magic. Let's see how many different meanings I can come up with.

Cards are those things that Wizards designs. For example, Grizzly Bears is a card, and Llanowar Elves is as well.

What about two Grizzly Bears? A card can also mean the physical object, sold in boosters and put in decks. But you can't even simply say that the physical card is "a Grizzly Bears", because there's a few different ones. And there's foil as well, and probably other things I'm forgetting. So the physical card is actually not an instance of what Wizards R&D designed, but of one translation of one printing of such a card, either in foil or not.

Getting to the actual game, cards are a kind of object, in contrast with tokens and copies of cards, which are not cards but serve almost the same purpose.

Noncard objects exist in a few different forms: emblems are always in the command zone; tokens can only exist on the battlefield; ability objects exist on the stack; copies of spells exist on the stack; casting a copy of a card creates that copy in the original card's zone, which in then put onto the stack as a spell while casting.

Permanents are objects that can be either cards or tokens, so another thing a card can be. Compared to other objects, permanents have state:  tapped/untapped, flipped/unflipped, face up/face down, and phased in/phased out.

The comprehensive rules on spells are worded a little strangely: "A spell is a card on the stack", "A copy of a spell is also a spell", "if the player does [cast a copy of a card], that copy is a spell as well". It sounds contradictory at first, but it's manageable.

So what have we got here:

• What Oracle says a card is, identified by the English name of the card.
• A printing of such a card, identified by English name together with an expansion. This extends the Oracle card by rarity, artist, illustration, collector number, card frame style, guild symbols and similar in the text box, ...
• A translation of a printing, identified by a multiverse ID, or alternately by English name, expansion and language; I wouldn't trust that the translated name is unique. The translation adds obviously anything language specific about a card. This includes printed, non-oracle wording including reminder text, as well as flavor text.
• A piece of cardboard that has a Magic card printed on it. To my understanding, this interpretation of "card" can be uniquely identified by a function defined on an interval of the timeline that maps every instant in that interval to the volume of space that is occupied by the card at that time. Or, a card is a card.
• A digital representation of such can also be considered a card in that sense.
• A card is an object that can be in a zone in a game of Magic.
• Some permanents are (represented by) cards.
• Some spells are (represented by) cards.

You can imagine that all this ambiguity makes it quite hard to come up with a proper software model for a game of Magic!

Trying out the card editor

I just tried out my card editor to download "a few" cards; all the vanilla creatures and old (non-pain) dual lands. If I haven't done anything wrong in my gatherer search, there are 177 vanilla creatures. it's in fact not so easy to search for textless cards; I had to use the regular expressing "m/^$/" ("m/.../" is the gatherer identifier for regexes, "^$" essentially means "the beginning of the text immediately followed by the end")

by the way, I haven't done a full fledged form for gatherer searches; I did the search on the web site and pasted the search URL into my program. takes me much less time^^

there were two problems: first, my download just discontinued after 89 cards. Looking at what card that was, it was Little Girl from Unhinged with a half mana symbol. Second, even after refining my search to exclude Un-cards, my program only wound up downloading 100 cards. my workaround for that problem was simply to download the other cards by reverting the sort order^^



so, putting things short, I now have over 200 cards implemented, including 177 vanilla creatures, 10 classic dual lands, 10 SHM/EVE dual lands, 5 basic lands, Wrath of God, Damnation and Llanowar Elves. It's really time for combat^^

The card editor

The last weeks had no updates in my main project, but there's a good reason for that. I worked on a card editor that lets you download gatherer card descriptions, edit them and lets you test if the card is correct.

I think I'll explain a bit more how Laterna Magica handles cards. A fundamental thought in my system was extensibility. I'm currently using a text format, but Laterna Magica allows you to use any format, even multiple ones at the same time. So, if I sometime see a reason to use e.g. XML, I can still use the old cards while developing cards for the new one.

A similar thought is true for the text format itself. It is key-value based, and every key is handled by its own class. If a line is "name Llanowar Elves", then the class for "name" gets the input "Llanowar Elves" and sets the name accordingly. If the line is "text {T}: Add {G} to your mana pool.", the "text" handler tries to find an ability parser that can parse the line. Even if I can't represent an ability, I can make a class specifically for that ability and add a line handler that applies an arbitrary class to the card, like "apply laterna.magica.cards.DestroyAllCreatures".

The output of the card parser is a CardTemplate object. All the CardTemplates created are stored in a zip file, so you can think of the card parser like a compiler: There's input of different types, like plain text and XML, but the parser(s) convert it into a uniform format that the program can work with (serialized java objects).
And here, my editor comes into play. After creating a card, the editor can directly feed it into the parser, which implicitly checks if all the lines in the file are correct. The card parser will ignore lines that can't be parsed (like "Dryad Arbor is green." in my last post), but the card creator (e.g. you^^) won't: You can see the parser's warning and correct the lines.

Basic editing, opening, saving and even downloading already works in the editor, but it still needs a few tweaks before it really has a benefit over normal text editors (which you will be more familiar with for sure):

• Compiling cards or creating the zip file doesn't work yet
• The card downloader does not convert a card's name, I would like to have "Shock deals two damage to target creature or player." as "~ deals two damage to target creature or player."
  Maybe even more complex transformations like "target((zone/battlefield & type/creature) | player)" ;)
  (that's just speculation. i have no idea how to do targets or even target parsing)
• There is a file system tree with all the cards, but currently you can't open a file by double-clicking it
• "Save As" should be possible by dragging an opened file (they are shown in a list) onto a folder in the tree.
• I want to display already opened/modified files with a different icon

Okay, the last one is just bells and whistles, but the others will really influence the usability. I have already created the shadowmoor hybrid lands, which was lots of copy/paste and changing names and colors. Although these cards are not parseable yet as-is, downloading the cards would have made it easier. It's not in the GUI yet, - currently, you can only download cards by multiverse-ID or card name - but the download functionality can use all of the strength of gatherer searching, so downloading exactly those ten hybrid lands shouldn't be too hard.

This editor is like a pet to me. I know I have better things to do - combat, namely - but right now I want to get this working.

Implementing some cards

Okay, I think I've spent enough time on how abilities work in my problem, but it's definitely easier when viewing some real cards.

In reality, I haven't done much of the work yet that would make making cards interesting - no targeting, no damage, no destruction or sacrificing - it's essentially creating and spending mana right now.

Before I come to the interesting cards which can't be done yet, I'll show you what already works in this post. I have done a simple parser for cards. In fact, it's quite extensible and can be configured to plug-in different file formats. The only file format by now is a plain text format, for which in turn different line-parsers can be plugged in.

And now to the cards:

name    Forest
super   basic
type    land - forest

The basic land types have the mana producing ability implied, which are also parsed as any other mana ability. I'm not sure how this will work with adding and removing basic land types, but it's like that for now.

name    Graven Cairns
type    land
text    {T}: Add {1} to your mana pool.
text    {B/R}, {T}: Add {B}{B} to your mana pool.
text    {B/R}, {T}: Add {B}{R} to your mana pool.
text    {B/R}, {T}: Add {R}{R} to your mana pool.

Right now, there are only activated abilities. Costs and Effect are parsed separately, and every cost is parsed on its own. By now, any combination of mana costs and Tap or untap costs are working. The only Effect is "Add ... to your mana pool." Things like "{B}{B}, {B}{R} or {R}{R}" are not possible by now, neither are hybrid symbols (they only work for costs), so I write it as three abilities.

name    Dryad Arbor
color   green
type    land - forest
type    creature - dryad
pt      1/1
text    (Dryad Arbor isn't a spell, it's affected by summoning sickness, and it has "{T}: Add {G} to your mana pool.")
text    Dryad Arbor is green.

Here you can see that every type is specified on its own line only with its corresponding subtypes. The two "text" lines here are actually nonfunctional. The "Dryad Arbor is green." Ability is actually implemented by the "color" line, and the mana ability comes from the forest subtype.